Electric safety plug



April 24, 1934. c ILBERT 1,956,018

ELECTRIC SAFETY PLUG I Fiied Aug. 20, 1950 gllflVENTdR WSRNEYS' Patented Apr. 24, 1934 PATENT OFFICE ELECTRIC SAFETY PLUG Charles E. Gilbert, New York, N. Y., assignor to Gilbert 3; Hertz, Inc., a corporation of New York Application August 20, 1930, Serial .No. 476,568 2 Claims. '(01. 173-361) This is a continuation in part of my application for United States Letters Patent No. 434,873, filed March 11, 1930.

Among the objects of this invention is that of obtaining an electric plug of cheap and rugged construction to which insulated electric wires may be easily and quickly connected without removal of the insulation on the wires, and which will hold such wires with great tenacity and with less danger of rupture than is obtained with plugs of usual construction.

My invention is particularly useful in the home, since lamp cords and the like may be easily and quickly attached thereto without the use of tools. Practically no skill or understanding of things electrical is required, whereas the proper attachment of wires to the kinds of plugs now in common use is a somewhat delicate and difllcult task for an unskilled person. If the wires are inseg'g curely or improperly connected, breakage or short-circuiting will soon occur. Actual tests of any plughave demonstrated that not only is proper attachment almost automatically secured by simply inserting the wires and assembling the plug, but also the wires will endure much greater abuse and strain before breaking away from the In the accompanying drawing I have selected two forms of my plug for purposes of illustration invention thereto.

Figure 1 is a side elevation of one form of the plug completely assembled Fig. 2 is a vertical cross section of the plug taken along the line A-A of Fig. 1;

Figs. 3, 4, and 5 are detail drawings of one of .the contact members;

Fig. 6 is a side elevation of another form of my plug assembled; 7 Fig. '7 is a verticalcross-sectional view of the 'plugofFlg.6; and Fig. 8 is a plan view of a modified contact member which may be employed, if desired, with either typ 0! plug. The character of the contact elements is clearly shown in Figs. 2 to 5. Each may be made from a single strip of, stiff but somewhat springy metal,

which is a good electrical conductor folded over upon itself, asbest shown in Figs. 2 and 3'. The end at which the fold occurs forms a prong 5 for insertion into the electrical socket or outlet. One of the two free ends 6 is bent inwardly and its edge '7 serrated to forms. wire-clamping jaw. A second similar jaw 8 may be obtained bybending inwardly a. square piece 9 of the strip 2, after first without thereby in any way intending to limit my cutting it away from the strip on the top and both sides. When these jaws 6 and 8 are forced towards the other side 9 of the contact member an insulated wire inserted therebetween will not only be securely held, but the insulation will be pierced by the serrated edges and excellent elec trical contact established. It will beobserved that the other free end 12 of the contact strip is also bent inwardly and a groove 13 formed in the edge thereof.

The object of. this construction is to provide a guide for the wire so that when it is in position a sharp bend in it will be produced between the clamping jaw 6 and the cable outlet 14, which materially assists in retaining the wire in position and renders it unnecessary to knot the wires just inside of the cap. The cap 3, also of nonconducting material, may be of any desired external shape; The interior thereof is conical, as

lated and which is entirely devoid of rivets, screws and other undesirable features.

Theplug is assembledand used as follows: The cap is slipped upon the electric cable in the usual way. The prong ends 5 of the'contact members are inserted in slots 11 in the body 1, which. slots correspond in shape to the cross section of prongs 5 and are just large enough to per-'- mit them to-be pushed'therethrough. The ends of the wires with the rubber insulation exposed are inserted in the grooves 12 and between the gripping jaws 6 and 8.

The contact members are then pushed completely into slots 11 until they assumethe position shown in Fig. 2, and the cap 3 is then screwed onto or. otherwise connected to the body to force the jaws 6 and.8 through the insulation and hold them securely in position. A very secure electrical connection is thus made withthe greatest ease and despatch and one which will stand a great deal of mistreatment.

The type of plug illustrated in Figs. 6 to 8 is based upon the same general principles. The contact members may be identical or, if desired, the end 12 may be provided with a'hole 15 instead of groove '13, which will make it easier to position the wires when attaching them. This same construction may, of course, be employed in the 7 type of plug first described.

. lower ends of which extend slots 17 similar to slots 11 in the first type oi plug, through which the prongs of the contact members pass. The cap 18 maybe in shape and general construc tion similar to the m type and may be equipped with any desired means for secure attachment to the body, such as threads or a bayonet joint.

This type diflers from the type of plug here tofore described, principally in that the cap plays no part in causing the contact mere to engage with the wires. in this instance pros h are inserted in the slots 17 through the recesses 16, leaving the jaw elements still projecting above the top of the body. The wires are then inserted through hole 15 and between jaws 6 and 8, and the contact members forced downward until the jaw portions are entirely contained within re= cesses 16. The width of recesses 16 is, of course, such that when the contact members are thus seated the jaws will be forced together sufficient- -ly to pierce the insulation and effect good electrical contact in the manner heretofore described. The cap is then placed in position upon the body.

To retain the contact members in the position described and as shown in Fig. 'i' it is desirable to equip the cap with a tubular extension 19 of nonconducting material of such length that it will substantially contact with the upper suriace or body 1 when the cap is in position and or such internal diameter that its edge will obstruct the entrances of recesses 16 sumciently to lock the contact members therein. If the cap is of metal tubular extension liiwill also serve as an insulator. If the cap is of bakelite or other non-conductor the extension may of course be molded in-' end of which comprises a prong for connection to a source of electricity, one free end of which constitutes a guide for an insulated wire and the other free end of which comprises a wire gripping and insulation piercing jaw in cooperative rele tion with said guiding end to establish electrical contact between the prong and the wire through the insulation thereof. 1

2. An electric safety plug comprising a body provided with removable contact members which expand upon removal to permit the placing oi insulated wires therein and contract upon insertion through contact with the body to grip said insulated wires, insulation piercing means upon said contact members, and means for maintaining said contact members in operative insulation piercing position within said body. 

